This invention relates to a videodisc playback method that repeatedly reproduces the prescribed number of tracks a multiple number of times.
In a videodisc playback system, conditions required for reproducing a prescribed set of pictures in multiple repetitions include: (1) the starting point for repeat playback and the starting point for return remain the same each time, and no shifting occurs; (2) return time is short, and even during the return period, the picture synchronization is not disturbed, thus permitting normal viewing; and (3) video muting during the return period is unnecessary. When the duration of the repeat period is short, and video muting is used, the on-time and off-time of the pictures are frequently repeated, causing flickering of pictures that makes viewing difficult.
Previously, when reproducing a prescribed set of pictures a multiple number of times, a method used was to repeat while searching corresponding pictures in the range by referring to the key-coded signals recorded on a videodisc. However, while searching for a key-coded signal, it is necessary to turn on video muting which cannot fully meet the above-mentioned condition (3), and, as mentioned above, it causes flickering pictures that make viewing difficult.
In the case of a fast playback method in which tracking is ignored and several tracks are jumped by using a limit of an optical system or tracking servo system, the tracking servo tends to slip off, and until the tracking servo is locked in again, the read signal that reads signals from the videodisc is missed, thus causing noise to mix in the picture and throwing the picture out of synchronization. Also, the number of tracks jumped in reading is irregular due to track deviation, thus, in the end, requiring the reference to the key-coded signals. Consequently, for the duration of jitter in the picture while searching for the key-coded signals, it always becomes necessary to turn on the video muting. In this case also, the shortcoming is that the condition (3) cannot be fully met, and because of the long period of time required for searching for the key-coded signals, the above-mentioned condition (2) cannot be satisfied, either.